The five-strand barbed wire fence in the foreground used to be all that separated the United States from Mexico, in the area of Sunland Park, N.M, But new fencing, seen in the background, was recently completed.

EL PASO  The number of people caught trying to sneak into the USA from Mexico is at its lowest level since the mid-1970s, signs of tougher enforcement and a weaker U.S. economy, officials say.

The Border Patrol caught 705,000 people along the U.S.-Mexico border in fiscal year 2008, which ended Sept. 30, according to new agency figures. That's nearly 2,000 a day and the lowest number since 1976, when 675,000 people were caught entering illegally between San Diego and southern Texas, the figures show.

The Border Patrol has long used the number of apprehensions as an indicator of how many people try to cross U.S. borders illegally. The latest figures show that recent steps — including building a fence, adding more Border Patrol agents and prosecuting more people caught sneaking across the border — are deterring illegal crossings, officials say. The weak U.S. economy also is discouraging migrants, officials and analysts say.

"We're definitely making it tougher on them," Border Patrol assistant chief Lloyd Easterling says. "I'm not telling you that we've won the war, but we are making headway."

Homeland Security Secretary Michael Chertoff said in a Dec. 19 speech that there's been "a collapse in the number of people who come across the border illegally."

Chertoff cited a weaker U.S. economy and "tough enforcement," including the addition of 6,000 Border Patrol agents since 2006 and the construction of 526 miles of fence along the U.S.-Mexico border since 2007. About 97% of illegal border crossers enter through Mexico, and about 90% are Mexican, Border Patrol figures show.

Josiah Heyman, a border expert at the University of Texas-El Paso, said that "economic conditions of the U.S. affect migration. Word gets back to Mexico really fast what the job opportunities are or are not," Heyman said. "It's possible we've crossed some threshold where it's risky and expensive to try to get to the U.S. (illegally) so it's beginning to discourage people." Illegal migrants often pay a smuggler about $2,000, Heyman said.

Border apprehensions have fluctuated widely for decades. They peaked at 1.7 million in the mid-1980s, fell to about 1 million in the late 1980s, and hit 1.6 million again in 2000. Border Patrol staffing has climbed steadily to 18,000 agents from 4,000 in 1993, agency figures show.

The Congressional Research Service said in May that the number of apprehensions is "the most reliable" measure of illegal crossings but doesn't give a full picture because "there are no reliable estimates" of those who evade capture. About 11.9 million illegal immigrants live in the USA, according to an October estimate by the Pew Hispanic Center.

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